1. Field of the Invention
The present invention relates to a ventilation structure in a vertically mounted motor which is attached to electric equipment for vehicles and the like.
2. Description of the Related Art
In general, conventional so-called vertically mounted type motors having core shafts oriented in the vertical direction are known. These vertically mounted motors have a case bracket forming a bottom portion of a motor casing and a lower end portion of the core shaft which projects downwardly through a lower case bracket to form an output shaft. A bearing located on an upper side of the lower case bracket for rotatably supporting the core shaft relative to the case bracket and a seal member located on a lower side of the lower case bracket to prevent the intrusion of foreign matters such as oil, dust and dirt are interposed between the case bracket and the lower end portion of the core shaft.
In these conventional vertically mounted and sealed motors, a ventilation path is defined in the motor casing to ensure that the pressure inside the casing is always equal to the ambient atmospheric pressure. The ventilation path is usually provided in the case bracket forming the bottom portion of the motor casing. However, because abrasion dust from a brush held in sliding contact with a commutator accumulates over an upper surface of the bottom portion of the motor casing, the ventilation path is likely to clog with the accumulated abrasion dust, which results in a failure to obtain a sufficient amount of ventilation in the motor casing.